DP83936AVF datasheet(12/104 Pages) NSC

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30 Functional Description

The SONIC-T

(Figure 3-1) consists of a twisted pair inter-

face (TPI) module an encoderdecoder (ENDEC) unit a

media access control (MAC) unit separate receive and

transmit FIFOs a system buffer management engine and a

user programmable system bus interface unit on a single

chip SONIC-T is highly pipelined providing maximum sys-

tem level performance This section provides a functional

overview of the SONIC-T

31 TWISTED PAIR INTERFACE MODULE

The TPI consists of five main logic functions

a the Smart Squelch which determines when valid data is

present on the differential receive inputs (RXIg)

b the Collision Detector which checks for simultaneous

transmission and reception of data on the differential

transmit output (TXOg) and differential receive input

(RXIg) pins

c the Link DetectorGenerator which checks the integrity

of the cable connecting the two twisted pair modules

d the Jabber which disables the transmitter if it attempts to

transmit a longer than legal packet and

e the Transmitter which utilizes a Transmit Driver and a

Pre-emphasis to transmit Manchester encoded data to

the twisted pair network via summing resistors and a

transformerfilter

Smart Squelch

The SONIC-T Controller implements an in-

telligent receive squelch on the RXIg differential inputs to

ensure that impulse noise on the receive inputs will not be

mistaken for a valid signal

The squelch circuitry employs a combination of amplitude

and timing mesurements to determine the validity of data on

the twisted pair inputs There are two voltage level options

for the smart squelch One mode 10BASE-T mode

(Figure

3-2) uses levels that meet the 10BASE-T specification The

second mode reduced squelch mode uses a lower squelch

threshold level and can be used in longer cable applica-

tions where smaller signal levels may be applied The

squelch level mode can be selected using the LOWSQL

input pin (see Section 20)

TLF12597 – 4

FIGURE 3-1 SONIC-T Block Diagram

TLF12597 – 5

FIGURE 3-2 Twisted Pair Squelch Waveform (10BASE-T Mode)

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